cos-tools: release cos-gpu-installer v2.7.3

BUG=b/516889734
TEST=Pull the container and test on a VM:
sudo COS_GPU_INSTALLER=gcr.io/<dev-project>/cos-gpu-installer:92fc3ff9 cos-extensions install gpu --  --gcs-download-bucket dev-nvidia-drivers --gcs-download-prefix R125-19216.395.15/227981a6-57fc-4095-9c69-ad5e7ac6087e --prepare-build-tools --host-dir /var/lib/nvidia7
Then test installation.
RELEASE_NOTE=none

Change-Id: I8d907f537cf5c24d63f91bf92f053f4ecb662651
Reviewed-on: https://cos-review.googlesource.com/c/cos/tools/+/154525
Tested-by: Miri Amarilio <mirilio@google.com>
Cloud-Build: 228075978874@cloudbuild.gserviceaccount.com <228075978874@cloudbuild.gserviceaccount.com>
Reviewed-by: Robert Kolchmeyer <rkolchmeyer@google.com>